(CBS/AP) SOFIA, Bulgaria - Israel vowed to strike back at Iran for a brazen daylight bombing Wednesday that killed at least seven people on a bus full of Israeli tourists in Bulgaria.

The bombing was the latest in a series of attacks attributed to Iran that have targeted Israelis and Jews overseas and threatened to escalate a shadow war between the two arch-enemies. Iran has denied involvement in the past but did not comment on Wednesday's attack.

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No group immediately claimed responsibility for the attack, which wounded 30 others. But suspicion immediately fell upon Iran and its Lebanese proxy, the Hezbollah guerrilla group.

"All signs point to Iran," Netanyahu said. "Just in the past few months, we have seen attempts by Iran to harm Israelis in Thailand, India, Georgia, Kenya, Cyprus and more. This is an Iranian terror attack that is spreading across the world. Israel will react forcefully to Iran's terror."